Knife sharpening apparatus



MayZO, 1947. E. w. CLARK KNIFE SHARPENING APPARATUS Fiied April 4, 1946 INVENTOR.

6M2 M/ M Patented May 20, 1947 UNITED STATES PATENT OFFICE 2,420,814 I KNIFE SHARPENING APPARATUS Earl W. Clark, Stuart, Fla.

Application April 4, 1946, Serial No. 659,494

6 Claims. (01. 51-116) My invention relates to improvements in a device for sharpening knife blades and more especially the re-sharpening of kitchen knives and the like which have been dulled in ordinary usage, wherein I preferably use cup shaped abrasive members made up of a disc and cup sides with segments of the cup sides removed so that the segments of the opposing abrasive member may inter-mesh. One of the objects of my invention is to provide abrasive members that may be retated on their axes. Another object is to provide a construction that substantially assures equal Wear on the grinding surfaces. A further object is to provide improved guiding for the knife blade.

I attain these and other objects by the mechanism illustrated in the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional elevation of the device taken on line l--l of Fig. 2. Fig. 2 is an end elevation of the device showing the crank end. Fig. 3 is a cross sectional elevation taken on line 33 of Fig. 1. Fig. 4 is a side elevation of the abrasive member. Fig. 5 is a sectional elevation of the abrasive member taken on line 5-5 of Fig. 4.

Similar numerals refer to similar parts throughout the several views.

The abrasive members I are made up of discs la and segments of cup sides lb, and are mounted on sleeves 2 which are cemented in abrasive members I; sleeves 2 are slidingly mounted on shaft 3. Shaft 3 is rotatingly mounted in frame 4 and crank 5 is provided to rotate shaft 3. Knife guides 6 are provided to properly position and guide the knife :blade and are made up of hubs 6a which are pressed on shaft 3, spokes 6b which radiate from hub 6a, outer rims? 6c, and abrasive member stops 6d. Helical springs "I bear against taper or cotter pins 8 in shaft 3 and against abrasiVe members I to yieldingly force said members against stops 6d. Fiber spacing ring 9 is provided to properly space knife guiding members 6 and to prevent the cutting edge of the knife blade II] from striking metal parts.

The grinding surfaces of the segments lb of the abrasive members I are beveled or inclined about twenty degrees with the vertical so'that the knife blade edge is sharpened to an included angle of about 40 degrees. This angle gives a sharp and durable edge.

The segments lb are made narrower than the space between adjacent segments so that segments of opposing abrasive members may intermesh and also so that the radial portions of knife guides 6 may be located therebetween. With this novel arrangement I obtain a maximum of knife blade guiding over the entire length of the blade and including the curved portion of the pointed end. Further, since the knife guides 6 are pressed or fastened on shaft 3, I am able to rotate the abrasive members by means of the knife guides B which reduces materially the bending stresses on the abrasive member segments. Since there will be relative motion between the abrasive members and the knife guides, I coat the sides of the segments lb with a paste made of Portland cement and water. This gives a smooth surface with a fairly low coefficient of friction so that parts 6b sustain only slight wear. Rims of knife guides are made as shown so that the knife blade may be sharpened up close to the knife handle when the abrasive members are not rotated. By rotating the abrasive members during the sharpening operation the grinding faces of the segments will all be worn down alike. However the knife blade may be sharpened without rotating the abrasive members, but to obtain a sharp edge with a minimum amount of grinding it is best to rotate the segments. Stops 6d are provided to osition the abrasive members properly so that the blade may wedge or force the opposing abrasive members apart at the start of the grinding operation. With my construction the springs 1 rotate with the shaft 3 and with the abrasive members and the abrasive members may slide freely on shaft 3 against or with the pressure of springs I. The maximum outward position of abrasive members I are indicated by dot and dash lines.

The abrasive members are made up of abrasive particles held together by a suitable binder. A metal disc may be substituted for the integral disc portion of the abrasive members shown in the drawings, in which case as is customary the metal disc may be moulded into the segments.

Springs 1 are made relatively long in proportion to the amount of compression so that the variation in pressure between the blade and the abrasive members is reduced to a reasonable amount.

In the knife sharpening operation, the abrasive members are rotated by means of the crank in one hand and the knife held in the other hand and the knife blade is drawn through the knife guides starting at the handle end and with a slight downward pressure. Or the blade may be pushed through the knife guides starting at the point of the knife. One pass through the knife guides should ordinarily sharpen the blade.

The above and other novel features are brought out in the subjoined claims.

What I claim is:

1. In a device for sharpening knife blades: cup shaped abrasive wheels each abrasive wheel being made up of a disc and cup sides and having a plurality of segments removed from said cup sides so that the segments remaining are narrower than the segments removed and said remaining segments having beveled grinding surfaces; a shaft on which said abrasive wheels are slidingly mounted; knife guiding means fixedly mounted on said shaft said means comprising a hub, a .plurality of spokes radiating from said hub, and abrasive wheel stops, said spokes being located between the segments of said abrasive wheels and forming guides for said knife blades and forming means by which said wheels are caused to rotate with said shaft; a frame for rotatingly mounting said shaft; springs mounted on said shaft wherein the said abrasive wheels are yieldingly forced against said wheel stops and wherein said wheels are forced apart by said knife blade when drawn between said knife guides and toward said shaft.

2. In a device for sharpening knife blades: cup shaped abrasive wheels each abrasive wheel being composed of a disc and cup sides said cup sides having a plurality of segments removed therefrom so that the segments remaining are narrower than those removed and said remaining segments having beveled grinding surfaces; a shaft on which said abrasive wheels are slidinglyv mounted; knife guiding means mounted on said shaft said means comprising, a hub, a plurality of spokes radiating therefrom, said spokes being located between the segments of said abrasive wheels and forming guides for said knife blades; abrasive wheel stops to properly position said wheels for starting the blade sharpening operation; a frame for mounting said shaft; springs acting against said abrasive wheels wherein said wheels are yieldingly forced against said stops and wherein said wheels are forced apart by said knife blad when drawn between said knife guides and toward said shaft.

3. In a knife sharpener: a frame comprising a base having upstanding portions at two opposite ends; a shaft journaled in said upstanding portions; knife guiding means mounted on said shaft and disposed substantially midway between said upstanding portions, said knife guiding means comprising two members spaced apart to guide a knife'blade therebetween, and each member comprising a hub and a plurality of spokes radiating therefrom; a pair of abrasive units oppositely disposed on each side of said knife guiding means and slidingly mounted on said shaft,-each of said oppositely disposed abrasive units comprising a hub portion'and a plurality of abrasive member portions disposed inspaced relationship and with their abrading faces obliquely inclined to the plane ofsaid knife guiding means, and abrasive member portions on one abrasive unit intermeshing with the abrasive member portions of the other abrasive unit, and the spokes of said knife guiding means disposed bet-ween adjacent abrasive member portions; abrasive unit positioning stops on said spokes; and spring means yieldingly forcing said abrasive units against said stops.

units oppositely disposed on each side of said knife guiding means and slidingly mounted on said shaft, each of said opposed abrasive units comprising a hub ortion and a plurality of abrasive member portions in spaced relationship with their abrading faces obliquely inclined to the plane of said knife guiding means, abrasive member portions on one abrasive unit intermeshing with the abrasive member portions of the other abrasive unit, and the spokes of said knife guiding means disposed between adjacent abrasive memer portions of said opposed abrasive units; abrasive unit stops on said spokes; spring means yieldingly forcing said abrasive units against said stops,said spring means mounted on said shaft.

5. In a knife sharpener: a frame comprising a bas having upstanding portions at two opposite ends; a shaft journaled in said upstanding portions; a pair of abrasive units oppositely disposed and slidingly mounted on said shaft, each of said opposed abrasive units comprising a hub portion and a plurality of abrasive member portions in spaced relationship and with their abrading faces obliquely inclined to a plane perpendicular to the longitudinal axis of said shaft, abrasive member portions on one abrasive unit intermes ing with the abrasive memberportions of the other abrasive unit; abrasive unit stops carried by said shaft; and spring means yieldingly forcing said abrasive units against said stops.

6. In a knife sharpener: a frame comprising a base having upstanding portions at two opposite ends; a shaft journaled in said upstanding Portions; a pair of abrasive units oppositely disposed and slidingly mounted on said shaft, each of said opposed abrasive units comprising a, hub portion and a plurality .of abrasive member portions in spaced relationship and with their abrading faces obliquely inclined to a plane perpendicular to the longitudinal axis of said shaft, abrasive member portions on one abrasive unit intermeshing with the abrasive member portions of the other abrasive unit; abrasive unit stops carried by said shaft; spring means mounted on said shaft and yieldingly forcing said abrasive units against said stops; a crank on said shaft; wherein said abrasive units, said stops and said spring means rotate with said shaft,

EARL W. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,068,973 Brown -1 July 29, 1913 1,415,375 Luebben May 9, 1922 1,699,510 Gaisman et al. Jan. 15, 1,929 2,114,106 Geveke Apr. 12, 1938 2,264,065 Broberg NOV. 25, 1941 

